As shown in FIGS. 44 and 45, in a strip blade material 1 that is to be used as a punching blade, a blade edge part 3 is formed in an edge in one side in the width direction of a strip plate part 2. After being subjected to a necessary bending work or the like, the blade material 1 is used in an application such as formation of a notch line or a fold line in a piece of paper, a sheet, a plate, or the like. In the blade material 1, end parts in the longitudinal direction are straight-cut as shown in FIG. 44, or miter-cut as shown in FIG. 45. As seen from FIG. 44, the straight-cut work is a work of linearly cutting end parts of the blade material 1 over the blade edge part 3 and the strip plate part 2. As seen from FIG. 45, the miter-cut work is a work of cutting end parts of the blade edge part 3 in the end parts of the blade material 1 into a shape which is obliquely inclined with respect to end parts of the strip plate part 2, and is conducted, for example, in order to prevent a gap from being formed in the blade edge portion when blade materials are joined to each other. In FIG. 45, miter parts of the blade edge are indicated by a reference numeral 3a. 
FIGS. 46 and 47 show the principle of a blade material cutting device which is conventionally known. The blade material cutting device comprises: a stationary blade part 5 having a slit 4 into which the blade material 1 is to be fed; and a movable blade part 6 which is laterally movable in front of the slit 4.
In the blade material cutting device, when the blade material 1 which has been fed as indicated by the arrow F in FIG. 47 is passed through the slit 4 of FIG. 46 and the feeding operation is stopped, for example, the movable blade part 6 is swung about a fulcrum f as indicated by the arrow a of FIG. 46. Then, a stationary edge 5a of the stationary blade part 5 and a movable edge 6a (see FIG. 48) of the movable blade part 6 cooperate with each other to cut the blade material 1. In this case, as shown in FIG. 47, the portion of the blade material 1 where the blade material 1 is overlaid on the stationary blade part 5, and by contrast the portion which is pressed by the movable blade part 6 is deformed in a side direction of the stationary edge 5a. After the cutting, the portion pressed by the movable blade part 6, therefore, the shape of the cut surface of the blade material 1 which is illustratively shown in FIG. 50A is bent as shown in FIG. 50B. By contrast, the portion supported by the stationary blade part 5, the shape of the cut surface of the blade material 1 shown in FIG. 50D is not deformed but is maintained to the original adequate shape as shown in FIG. 50C. When, in portion where the operation of feeding the long blade material 1 is stopped, a predetermined portion of the blade material 1 is cut by using the blade material cutting device shown in FIGS. 46 and 47, therefore, the cut surface shape of the front end 1a of the blade material 1 which is produced as a result of the cutting is not deformed but is maintained to the original adequate shape as shown in FIG. 51, but that of the rear end 1b of the blade material 1 which is produced as a result of the cutting is bent. Also a portion W in the vicinity of the rear end 1b is similarly bent.
When the blade material 1 is to be cut, the strip plate part 2 and the blade edge part 3 of the blade material 1 must be overlaid on a support face 7 formed in the stationary blade part 5 as shown in FIG. 49. When the blade edge part 3 is not overlaid on the support face 7, particularly, the blade edge part 3 is bent.
When the straight-cut work shown in FIG. 44 or the miter-cut work shown in FIG. 45 is requested to be conducted, edges of the stationary blade part and the movable blade part must be formed into a shape which enables such a work.
FIGS. 52, 53, 55, and 56 show a blade material cutting device which can conduct the above-mentioned two kinds of cut works.
In the blade material cutting device, support faces 7a, 7b are formed respectively in right and left side faces of the stationary blade part 5, a stationary edge of the support face 7a on one side serves as a straight-cutting edge, and that of the support face 7b on the other side serves as a miter-cutting edge.
In the blade material cutting device, when the stationary edge for straight-cutting and a movable edge of a movable blade part 6 cooperate with each other to cut two or front and rear portions of the blade material 1 as shown in FIGS. 52 and 53, the front end 1a of the blade material 1 which is produced as a result of the cutting is not deformed but is maintained to the original adequate shape as shown in FIGS. 54A and 54B, but the rear end 1b of the blade material 1 which is produced as a result of the cutting is bent as shown in FIGS. 54C and 54D. In the blade material cutting device, also when the stationary edge for miter-cutting and the movable edge of the movable blade part 6 cooperate with each other to cut two or front and rear portions of the blade material 1 as shown in FIGS. 55 and 56, the front end 1a of the blade material 1 which is produced as a result of the cutting is not deformed but is maintained to the original adequate shape as shown in FIGS. 57A and 57B, but the rear end 1b of the blade material 1 which is produced as a result of the cutting is bent as shown in FIGS. 57C and 57D.
FIGS. 58 to 61 show another blade material cutting device which can conduct the above-mentioned two kinds of cut works.
In the blade material cutting device, the stationary blade part 5 is formed into a fork-like shape having a pair of right and left protrusions 8, 9. The above-mentioned support faces 7a, 7b are formed respectively in opposed left and right side faces of the pair of protrusions 8, 9, a stationary edge of the support face 7a on one side serves as a straight-cutting edge, and that of the support face 7b on the other side serves as a miter-cutting edge.
In the blade material cutting device, when the stationary edge for straight-cutting and a movable edge of the movable blade part 6 cooperate with each other to cut two or front and rear portions of the blade material 1 as shown in FIGS. 58 and 59, the front end 1a of the blade material 1 which is produced as a result of the cutting is not deformed but is maintained to the original adequate shape in the same manner as described with reference to FIGS. 57A and 57B, but the rear end 1b of the blade material 1 which is produced as a result of the cutting is bent in the same manner as described with reference to FIGS. 57C and 57D. In the blade material cutting device, also when the stationary edge for miter-cutting and the movable edge of the movable blade part 6 cooperate with each other to cut two or front and rear portions of the blade material 1 as shown in FIGS. 60 and 61, the front end 1a of the blade material 1 which is produced as a result of the cutting is not deformed but is maintained to the original adequate shape, but the rear end 1b of the blade material 1 which is produced as a result of the cutting is bent.
FIGS. 60 and 61 which have been described above show an example in which the blade material 1 is cut into a miter shape wherein an end part of the blade edge part 3 after the cutting is inclined in a direction along which the end part does not protrude from the strip plate part 2. In contrast, FIGS. 62 and 63 show an example in which the blade material 1 is cut into a miter shape wherein an end part of the blade edge part 3 after the cutting is inclined in a direction along which the end part protrudes from the strip plate part 2.
In the above-described blade material cutting devices, in the same manner as the conventional blade material cutting device which has been described with reference to FIGS. 46 and 47, there is a problem in that the front end 1a of the blade material 1 which is produced as a result of the cutting is maintained to the original adequate shape, but the rear end 1b of the blade material 1 which is produced as a result of the cutting is bent.